Apparatus for comminuting materials have application to a number of industries, which may involve shredding of wood, bales of hay or paper, comminuting bitumen, plastic, metal or other materials. An effective comminuting apparatus has a high throughput, does not jam often, is reliable, easy to maintain, is energy efficient and comminutes relatively uniformly
Tub grinders are well known devices for grinding various materials. Vertical feed tub grinders have the advantage of using gravity to force the material onto the rotor, reducing or eliminating the need for further conveying means for the material other than that required to feed the material into the tub. However, one problem with tub grinders is their tendency to jam.
Another problem with known tub grinders at present is apparent when they are used to comminute lighter material such as paper. The turbulence, vortices and movement of the rotor against the material tends to force the material upwards. Therefore, intervention may be required to force the material onto the rotor and through the screens.
A comminuting apparatus including a rotating tub is described in the specifications of U.S. Pat. Nos. 5,379,951 and 5,927,624. Within the tub is mounted a toothed disc that preferably rotates in the opposite direction to the tub. The problem of potential jamming is stated to be overcome or reduced by reversing the direction of rotation of the toothed disc and/or by providing a reorienting attachment secured to the bottom of the chamber defined by the tub. However, such a comminuting apparatus may still be susceptible to jamming.
It is an object of the present invention to provide a comminuting apparatus that may be freed from jamming, optionally automatically and/or has improved operation for lighter materials.
It is a further or alternative object of the present invention to provide the public with a useful alternative.
Further objects of the present invention may become apparent from the following description.